Hi.
How many rows of conditional : CREDIT_ID IS NOT NULL?
1) The condition WHERE TJ1.CREDIT_ID IS NOT NULL is superfluous.
PDML in MERGE operator doesn't work
2) PDML can not work. There are restrictions
3) May be to use dbms_parallel_execution ?

Hi.
I am glad that you achieved result.
But,it is very interesting that there are 83 percent quicker )))
Can you provide plans of queries with execution statistics: before optimization and after optimization?
Which is results: how changed the plan, how changed the DB_TIME and etc ?
For analyse plan of your query is possible to use v$active_session_history/v$sql_plan_statistics and etc ... or EM.